Research on VSG control of grid-structured parallel fed inverter based on improved virtual synchronous generator
With the high proportion of new energy connected to power grid,multi-machine parallel coordinated control of energy storage inverter has become a key problem.Virtual synchronous generator(VSG)algorithm can provide damping,inertial support and stable voltage frequency for grid-forming energy storage system.However,the parallel synchronization,stability,state of charge(SOC)of each stack and impedance of each line should be considered in the coordinated control of parallel operation of multiple energy storage inverters.To solve this problem,a parallel mathematical model of energy storage inverter is established,the methods of reactive power allocation considering virtual impedance and active power allocation considering SOC are analyzed,and an improved VSG control strategy combining self-adaptive virtual impedance and SOC equalization is proposed.Finally,a model is built on the MATLAB/Simulink simulation platform,and the coordination control of each energy storage inverter is analyzed under the discharge condition with the all vanadium redox flow battery pack as the energy storage system.The validity of the improved VSG control strategy is verified,and the problem of over-discharge caused by voltage drop,reactive power and SOC difference caused by impedance difference is solved effectively,the utilization efficiency of the battery and the energy storage inverter is improved,and the life loss of the battery is reduced.
grid-forming energy storage inverterVSG controlself-adaptive virtual impedanceSOC equalizationparallel operation
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